I rarely line my holsters, and then only with a thin lining kip. If lining holsters you want a thin smooth leather so that your pistol will come easily out of the holster. I usualy make my holsters unlined. If you want it to be slick use Gum Tracangth it will make the holster slick on the inside and not hurt your leather or your pistol. You can also use it on the edges of leather before you burninsh them for a slick smooth edge. Saddlemakers have been using it for over a hundred years.